Domains can operate at various functional levels: Windows 2000 mixed, Windows 2000 native, and Windows Server 2003 (which only includes domain controllers running Windows Server 2003), Windows Server 2008, and Windows Server 2008 R2.
Once all domain controllers are running a newer version of Windows Server, you can raise the Domain and Forest Functionality to Windows Server by opening Active Directory Domains and Trusts, right clicking the domain for which you want to raise functionality, and then clicking Raise Domain Functional Level.
Note that once you raise the domain functional level, domain controllers running earlier operating systems cannot be introduced into the domain. For example, if you raise the domain functional level to Windows Server 2003, domain controllers running Windows 2000 Server cannot be added to that domain. However such servers can be members of the domain.
Table 3 Forest-wide Features Enabled for Corresponding Forest Functional Level
The deployment of an operating system in any organization is a very large project. Application compatibility with the new operating system is one of the most critical steps in the testing and planning phases of a successful deployment. This entails verifying that all existing software and any planned software will function correctly on the new operating system at least as well as it did on the old operating system.
The benefits of upgrading applications running on Windows Server 2000 to Windows Server 2008 R2
Windows Server 2008 R2 includes all of the features of an enterprise class application server. Windows Server 2008 R2 application and web platform enhancements provide many benefits for developing applications including:
Identify applications that might have a compatibility issue by verifying whether the ISV who created the application supports or has logoed the application(s) on a newer version of the operating system. (The Windows Server Catalog contains a list of all ISVs that have pledged to support their apps on Windows Server 2008 R2 as well as a list of all logoed applications)
If an application is not supported or logoed on Windows Server 2008 R2, contact the ISV to obtain a new version of the application that runs on the new operating system or request support for your obsolete application.
If the ISV does not support their application on newer versions of Windows Server, or if you are unable to determine the ISV’s policy, you may still assess your application's compatibility, security, stability, reliability and availability in a Windows Server 2008 R2 environment by taking advantage of Microsoft’s free self-test tools and resources listed below.
Prepare for an application upgrade by reviewing the links and resources listed below. Ease the process by identifying and eliminating problems before upgrading.
Upgrade and deploy with confidence.
Migrating custom applications
Make an inventory of, and prioritize, applications.
Download the free test tools and resources to assess your application’s compatibility on newer versions of Windows Server.
Create a test plan for all applications that need to run on the upgraded servers.
Empower your build/test teams with more comprehensive test scenarios based on Microsoft’s application development/testing standards and recommended upgrade practices. Test tools such as the Application Compatibility Toolkit (ACT Version 5.5) and Software Certification Toolkit may also be used as black-box evaluators to identify any potential compatibility issues.
Create a remediation plan if needed to update your applications. Learn about Windows Server 2008 R2 application and web platform enhancements such as:
Build More Flexible Web Applications: Internet Information Server 7.5, PHP optimized, ASP .NET on Server Core, Enhanced FTP and WebDAV
Build Connected Systems: Windows Communication/Workflow Foundation, Windows Process Activation Service, Microsoft Message Queue
Build Scalable Applications: Support for up to 256 logical processors, NUMA support, Thread Pool, Thread Ordering Service